To ensure the safe operation of devices with containers containing a pressurized gas, such as hydraulic accumulators, among other things, all risks which can arise at the installation site of these devices must also be considered. Possible hazardous external effects are important, especially temperature spikes that occur in a fire in the immediate vicinity of these gas-pressurized containers and that can lead to the failure of the container.
DE 32 19 526 A1 discloses a safety device for these pressure vessels, in particular for lightweight metal pressure vessels for liquefied gas. The safety device is formed essentially by a fusible screw threaded in a flange of the pressure vessel. The fusible screw contains a metal alloy with a low melting point, with the metal alloy being disposed in an exit channel for pressurized liquefied gas. The fusible alloy is covered by a metal foil ensuring tightness during alternating loads in operation of the pressure vessel.
In normal operation, the safety device is disposed in a region surrounded by fluid so that its temperature is defined. In the event of a fire, it can be assumed that the liquefied gas will undergo transition into the gaseous phase and the fusible alloy will thus be heated, as a result of which pressure equalization to the outside is enabled. An explosion of the pressure vessel is avoided in this way. However, the vicinity of the pressure vessel can be adversely affected or endangered by the rapidly emerging hot and liquid fusible alloy.
U.S. Pat. No. 6,367,499 B2 discloses a safety device for pressure vessels disposed in a relief opening of a gas pressure vessel. A piston-like closure element which is disposed axially in an outflow opening from the gas pressure vessel to the outside with an energy storage mechanism for opening of the outflow opening. The closure element is pressed against a stop of fusible material. The stop constitutes a heat-sensitive relief device. Under the action of heat, the molten material of the stop can escape radially from the safety device so that the closure element clears the outflow opening. A radial escape of the fusible material constitutes a safety increase in the known safety device.